Superconducting Properties in Metallic Phase of NbS3

Metallic phase of NbS₃ was synthesized by heating the crystal of semiconducting NbS₃. Metallic NbS₃ undergoes superconducting transition around 2 K. The analysis of the angular dependence of the upper critical magnetic field suggests that the effect of filmy or fibrous morphology plays an important role in the superconducting properties.     

Superconducting Transition of (TMTSF)2CLO4 in Magnetic Fields

Abstract

Superconducting transition of (TMTSF)₂ClO₄ was studied by conductivity measurements along the most conductive a-axis in magnetic fields applied along three different principal crystallographic axes. The GL coherence lengths at OK along the a-, b-, and c*-axes, ?_a(0)≈ 600A, ?(0) ≈ 540A, and ?_c*(0) ≈ 60A were obtained from the measurements of the temperature dependence of the upper critical field H_C2 near the transition temperature. The anisotropy is discussed in terms of the dimensionality arising from the crystal structure and of the conductivity anisotropy in the normal state.     

吡嗪席夫碱银配位聚合物的晶体结构、发光性质和抗菌活性

利用2-乙酰基吡嗪和异烟肼在无水乙醇中反应得到席夫碱化合物N-[(1-吡嗪基)-1-亚甲基]异烟酰肼(L).以L和硝酸银为原料,通过扩散法合成了配位聚合物{[Ag3L2(NO3)2]CH3CN}n,并通过X-射线单晶衍射、元素分析、红外光谱、荧光光谱对其进行结构解析和性质表征.单晶衍射分析结果表明,该配位聚合物属单斜晶...     

Silver (I) coordination by 1-(t-butyl)-2-benzoylaziridine

The reaction between AgNO₃ and 1-(t-butyl)-2-benzoylaziridine (tBBA) leads to the formation of bis-(1-(t-butyl)-2-benzoylaziridine) nitrato silver (I) which is a new metal aziridine derivative. The crystal structure was established by X-ray diffraction. [Ag(tBBA)₂(NO₃)] crystallizes in space groupC222₁ witha=11.877(6),b=13.560(4),c=16.923(4)Å andZ=4. The silver atom is six-coordinated by two N atoms of two aziridine rings (Ag-N=2.39(1)Å), two O atoms of two benzoyl groups (Ag-O=2.60(1)Å) and two O atoms of the nitrato group (Ag-O=2,60(1) Å). The coordination around the silver atom defines a very distorted octahedron with the C2 symmetry. The twofold axis passes through one O and the N nitrato atoms, and the silver atom. The nitrato group and tBBA act as bidentate ligands. These results are in contrast with our previous studies on aziridine zinc (II) complexation where the zinc atom is not coordinated by the benzoyl group.     

(1-4x)NBT-3xKBT-xBT系压电陶瓷电性能研究

采用传统固相法制备了(1-4x)NBT-3xKBT-xBT(x=0.020～0.035)体系压电陶瓷.采用XRD分析发现该体系陶瓷都能形成单一的钙钛矿型固溶体,并在0.025≤x≤0.032范围内具有三方和四方共存结构,为该体系的准同型相界.当x=0.028时,d33=162 pC/N,Qm=203.29,kp=0.234.电滞回线分析表明,(1-4x)NBT-3xKBT-xBT体系陶瓷随着KBT和BT含量的增加具有从铁电体向反铁电体转变的趋势.     

CeO_2缓冲层热处理对Tl-2212薄膜超导特性的影响

本文采用原子力显微镜(AFM)和XRD研究了生长在蓝宝石(11-02)基片上的CeO_2缓冲层在不同的退火温度和退火时间下表面形貌和相结构的变化,以及对Tl-2212薄膜超导特性的影响.AFM和XRD研究表明,CeO_2薄膜在流动氧环境中退火,表面形貌发生显著的变化;CeO_2薄膜在最佳条件下退火后,可获得原子级光滑表面,结晶质量明显提高.实验结果表明,缓冲层的结晶质量和表面粗糙度与Tl-2212薄膜的超导特性密切相关.在经过最佳条件退火后的CeO_2缓冲层上制备了厚度为500 nm无裂纹的Tl-2212超导薄膜,其临界转变温度(T_c)达到107 K,液氮温度下临界电流密度(J_c)为3.9 MA/cm~2(77 K,0 T),微波表面电阻(R_s)约为281 μΩ(77 K,10 GHz).     

Resistive and Magnetic Susceptibility Transitions in Superconducting (TMTSF)2C104

We report measurements of the ac magnetic susceptibility and dc resistive superconducting transitions in the organic superconductor (TMTSF)₂C10₄. Inductive measurements show complete diamagnetic shielding below a broad transition and initial flux penetration at very low fields [H_c1(0) < 1 Oe]. The resistive transition is also broad, but occurs at a significantly higher temperature than the inductive transition, T_c = 1.0 K and 0.65 K respectively. Resistance measurements also show evidence of a phase transition in the vicinity of 24 K. Magnetic field induced transitions, measured both inductively and resistively, show marked anistropy both in magnitude and in breadth of the transition. Results suggest that (TMTSF)₂C10₄ is a quasi ID or 2D superconductor at high temperatures and high magnetic fields and an anisotropic bulk superconductor at low temperatures and fields. Associated thermoelectric power measurements suggest that spin density waves coexist with the superconducting state.     

稀HNO3对银纳米线薄膜电极光电性能影响的研究

本文以自制的银纳米线分散液为镀膜前驱体,利用不锈钢棒在聚对苯二甲酸乙二酯(PET)基底表面制备银纳米线薄膜电极,讨论HNO3溶液的浓度和处理时间对薄膜光电性能与表面形貌的影响.结果表明,当利用浓度为1:50(浓HNO3与蒸馏水体积比)的稀HNO3溶液处理薄膜30 min时,银纳米线薄膜的方块电阻可降低95;～97;,而薄膜的可见光透过率则提高3;～4;.     

Effect of Lithium Doping in the Bi-2212 Superconducting System

Samples with the nominal composition Bi₂Sr₂Ca_1–xLi_xCu₂O_y (x = 0.2,0.4, and 0.6) and Bi₂Sr₂CaCu_2−x L1_xO_z (x = 0.4, 0.6, and 1.0) were prepared by the solid state reaction method. The role of L1 at both Ca and Cu sites in the Bi-2212 composition were studied. From the X-ray diffraction data it was found that the L1-doped at the Ca site increases the c-axis and that doped at the Cu site decreases the c-axis. From the D.C. four-probe resistivity data it was found that Li-doped at the Ca site reduces the T_c and the L1-doped at the Cu site gives T_c(0) above the liquid nitrogen temperature. It was observed that the L1 doping reduces the melting point of Bi-2212 composition. The presence of Lithium was confirmed by inductive the coupled plasma method.     

氧分压对Bi-2223/Ag/Ni带材中Bi-2223相形成的影响研究

在Bi-2223相的生成过程中,氧起到非常重要的作用.对Bi-2223/Ag带材而言,氧能够透过银包套在超导芯与外部环境气氛之间进行交换,因而,超导芯处的氧与气氛中氧含量相近.而对于Bi-2223/Ag/Ni带材而言,外层的包套材料为镍,氧不能扩散通过镍包套.为了使氧能够在超导芯与环境气氛之间进行交换,将带材一侧的镍去除,为氧的扩散提供一个通道.这使得氧在Bi-2223/Ag带材与Bi-2223/Ag/Ni带材中扩散条件和扩散过程是完全不同的,超导芯的氧含量的变化规律也是不一样的,必然会对Bi-2223相的生成过程产生影响.实验结果表明,在单芯Bi-2223/Ag/Ni带材中,高的氧分压不利于Bi-2223相的生成.     

银纳米颗粒表面覆盖度对非晶硅薄膜光吸收特性的影响

本文采用磁控溅射系统在非晶硅薄膜的表面沉积不同覆盖度的银纳米颗粒,并研究纳米颗粒的表面覆盖度对非晶硅薄膜光吸收特性的影响.结果表明随着纳米颗粒表面覆盖度的增加,薄膜的晶格结构并不受影响.但是,随着表面覆盖度的增加,薄膜在近红外区域内对光的吸收范围却发生了明显变化.当纳米颗粒的表面覆盖度达到8;时,薄膜在近红外区域内对光的吸收范围达到了最大.这主要是由于纳米颗粒的局域表面等离子体增强了光吸收.     

Optical Properties of Poly(Isothianaphthene)

Abstract

The optical properties in poly(isothianaphthene), PITN, have been investigated by photoconductivity measurements and in situ optical absorption spectroscopy measurements during electrochemical n-type doping. Irradiation of the anode induces photoconductive response for a photon energy neighboring the band-gap and upon irradiation of the cathode photoconduction was observed for light of photon energies higher than the band-gap. The origin of this anomalous polarity effect of photoconduction in PITN has been discussed.     

热分解工艺对溶胶-凝胶法制备Tl-2212超导薄膜特性的影响

研究了在铝酸镧(LAO)基片上TBCCO凝胶膜的热分解条件对Tl2Ba2 CaCu2O8(Tl-2212)薄膜的结晶质量、表面形貌、组分比例的影响.SEM和XRD研究表明,凝胶膜经过适当条件热分解后,可以制作出具有致密的晶体结构、高度c轴取向的外延Tl-2212超导薄膜,其薄膜具有较好的电学性能.其临界温度Tc可达106 K,临界电流密度Jc可达0.83 MA/cm2 (77 K,0T).     

石墨烯/银纳米线复合透明导电薄膜光电性能及稳定性研究

利用旋涂法和机械转移法在柔性衬底聚对苯二甲酸乙二酯(PET)基板表面构建石墨烯/银纳米线复合透明导电薄膜.复合薄膜具有优良的电学性能,在可见光550 nm处透过率为73.2;,薄膜面电阻低至0.32 Ω/□.与银纳米线薄膜相比,石墨烯/银纳米线复合薄膜还表现出良好的电学稳定性,在90天后银纳米线薄膜面电阻增加率高达648;,而复合薄膜面电阻的增加率仅为30;.此外,在270天后,复合薄膜在循环弯曲300次前后,与LED灯串联可获得恒定的输出电压,表现出良好的机械弯曲稳定性.     

Pressure Dependence of the Metal-Insulator and Superconducting Phase Transitions in (TMTSF)2 Reo4

Measurements of the pressure and temperature dependence of the a-axis resistivity of (TMTSF) ₂ReO₄, are presented. The metal-insulator transition seen in this material at the remarkably high temperature of ～180 K at ambient pressure and which is associated with an ordering of the ReO₄, anions is suppressed under pressure. For pressures above ～9.5 kbar we observe a superconducting transition near 1.3 K. There is a narrow intermediate pressure regime about 2.5 kbar in width in which both superconductivity and effects of anion ordering are observed. In this regime (i) a superconducting transition is seen near 1.3 K even though ρ just above the transition can be up to 10-100 times greater than ρ(300 K), and (ii) there is an extraordinarily large hysteresis in p below ～ 100 K with the possibility of varying the resistance of the low temperature state by several orders of magnitude by appropriate temperature cycling. These results establish the first order character of the transition. We suggest that at high pressures the anions remain frozen in a metastable disordered state to low temperatures.     

X-Ray Diffuse Scattering Study of Anisotropy of Elastic Properties in Silver Thiogallate

Measurements of the diffuse X-ray scattering intensity are performed from the (100) and (001) planes in the AgGaS₂ compound with tetragonal chalcopyrite-type structure. From these data the phase velocities of elastic waves along the principal symmetry directions for longitudinal and transverse polarizations as well as all six elastic moduli C_ik are found. The comparative analysis of both the anisotropy of the thermal diffuse scattering intensity distribution and the character of the elastic anisotropy for the ternary compound AgGaS₂ with the chalcopyrite structure and the binary analogs CdS and ZnS with the sphalerite structure is carried out.     

YBCO/ND-Y2O3/YBCO超导薄膜的制备及其特性研究

采用光辅助金属有机物化学气相沉积技术,在LaAlO3(100)单晶衬底上外延制备约500 nm厚YBCO/ND-Y2O3/YBCO薄膜.用X射线衍射技术分析薄膜的物相结构和外延特性,通过扫描电子显微镜观察薄膜的表面与截面形貌.主要研究了不同生长时间的Y2 O3纳米点对YBCO超导薄膜性能的影响.Y2 O3纳米点生长时间为2Os样品的临界电流密度达到2.4 MA/cm2(77 K,0T),与未生长Y2O3纳米点的YBCO薄膜相比,其临界电流密度提高20;.分析表明,薄膜中的Y2O3在YBCO薄膜内部起到了有效钉扎中心作用,提高了临界电流密度.     

CdZnTe(211)面纳米力学特性分析

采用研磨-机械抛光-化学机械抛光工艺对CdZnTe(211)面进行加工,当表面粗糙度Ra达到0.94 nm时,采用纳米压痕仪对CdZnTe(211)面进行纳米力学性能测量,试验结果表明:弹性模量和硬度随着压力的增大而减小,存在明显的尺寸效应.当针尖离开晶体表面时,黏附现象特别明显.在不同晶向上,弹性模量和硬度存在显著的各向异性.     

Mg3(Si1-xCex)2O7系复合陶瓷微波介电性能研究

采用固相反应法按式Mg3(Si1-xCex)2O7(x=0.2,0.3,0.4和0.5)制备了MgO-SiO2-CeO2系列微波介质陶瓷材料,研究了不同组分体系的相组成与结构、微观结构与微波介电性能之间的影响关系.结果显示:MgO-SiO2-CeO2体系在研究组分范围内的晶相主要由正交相的Mg2SiO4与立方相的CeO2组成;其中,当x=0.5时出现了少量的未知相;经EDS分析可知,该未知相是由Mg、Si、Ce和O元素组成的新相;随着x值的增加,体系εr和τf值在1350～1600℃烧结温度下的变化不明显,而体系的Q×f值则呈先降后升趋势.此外,尽管体系并未能确定形成RP相层状结构,但其研究结果仍对探索新型RP相微波介质材料具有借鉴作用.     

Critical aspects on preparation of Bi-2223 glassy precursor by melt-process

It is well known that many Bi–Sr–Ca–Cu–O compositions are glass forming and are converted into high-critical temperature superconductors after proper annealing. Glassy precursors have been prepared by rapid quenching of nominal Bi₂Sr₂Ca₂Cu₃O₁₀ melts from above 1000 °C in air using different conditions. In order to fabricate superconductors having high-critical temperature and current density using the glass–ceramic route, it is necessary to clarify the total chemical composition of the quenched glasses. For the first time the total chemical composition of such melts has been directly investigated by element analysis. The oxygen content has been directly measured by carrier gas hot extraction of as-quenched melts. The investigated cation content in as-quenched nominal Bi₂Sr₂Ca₂Cu₃O₁₀ melts presents significant deviations in composition for the glassy precursor, foremost for the calcium content. The main reasons of the non-complete transition from nominal to obtained composition after the quenching step was showed to be due to inhomogeneous and incomplete melting. This dependency is showed to be highly affected by the nominal composition of the melt. From literature there are barely any published values of the chemical composition of the quenched glassy precursors that would however be critical to control the crystallization behavior and to understand the influences on the superconductive properties.